43 research outputs found
Maximal Tukey types, P-ideals and the weak Rudin-Keisler order
In this paper, we study some new examples of ideals on with maximal
Tukey type (that is, maximal among partial orders of size continuum). This
discussion segues into an examination of a refinement of the Tukey order --
known as the "weak Rudin-Keisler order" -- and its structure when restricted to
these ideals of maximal Tukey type. Mirroring a result of Fremlin on the Tukey
order, we also show that there is an analytic P-ideal above all other analytic
P-ideals in the weak Rudin-Keisler.Comment: 17 page
Classifying the Arithmetical Complexity of Teaching Models
This paper classifies the complexity of various teaching models by their
position in the arithmetical hierarchy. In particular, we determine the
arithmetical complexity of the index sets of the following classes: (1) the
class of uniformly r.e. families with finite teaching dimension, and (2) the
class of uniformly r.e. families with finite positive recursive teaching
dimension witnessed by a uniformly r.e. teaching sequence. We also derive the
arithmetical complexity of several other decision problems in teaching, such as
the problem of deciding, given an effective coding of all uniformly r.e. families, any such that
, any and , whether or not the
teaching dimension of with respect to is upper bounded
by .Comment: 15 pages in International Conference on Algorithmic Learning Theory,
201
Patterns and Mechanisms of Ancestral Histone Protein Inheritance in Budding Yeast
Tracking of ancestral histone proteins over multiple generations of genome
replication in yeast reveals that old histones move along genes from 3β²
toward 5β² over time, and that maternal histones move up to around 400 bp
during genomic replication